CLA.RK: AUSTRALIAN AND INDO-PACIFIC ECHINODEEMS. 115 



Arm-spines short, rarely (except lowest) exceeding joint (in 

 Pectinura danb>/i nearly twice as long as joint) more or 

 less closely appressed to arm. 

 Eadial shields covered by granulation of disc. 

 Disc more or less notched at insertion of arm; marginal 



scales not enlarged or visible through granulation . . Pectinura 

 Disc not notched at insertion of arms ; marginal scales 



enlarged, conspicuous underneath granulation .... Opkiopezella 

 Radial shields not covered by granulation of disc. 



Radial shields very large ; interradial space between 

 two little wider than radial ; interbrachial areas 



(orally) narrower than arm-bases Ophiochasma 



Radial shields small or of moderate size ; interradial 

 space between two much wider than radial; inter- 

 brachial areas (orally) wider than arm-bases .... Ophiarachnella 

 Arm-spines long, 1—3 times as long as joint, more or less flaring ; 



supplementary oral plates present in interbrachial areas . . Ophiarachna 

 Tentacle-scale single, very large (one or two additional may 

 be present on some basal pores) ; supplementary oral plates 



rudimentary or wholly wanting Bathyptctinura 



Oral shields more or less completely concealed by granulation of 

 interbrachial area; tentacle-scale single ; arm-spines very short, 

 appressed Cryptopelta 



Pectinura. 



Forbes, 1842. Trans. Linn. Soc, London, 19, p. 143. 

 Type-species, vestita Forbes, 1. c. Monotypic at the time. 



Synonyms: Ophiopeza Peters, 1851. Monatsb. Kon. Ak. Berlin, p. 46-5. Based on 

 O.fallnx Peters(l. c.) and supposed to be distinguished by absence of 

 supplementary oral plates. This character having been shown to 

 lack generic value, O.fallax is here placed, because of its hidden 

 radial shields, in Pectinura ; Ophiopeza thus becomes a pure 

 synonym. 

 Ophiopsammus Liitken, 1869. Add. Hist. Oph., 3, p. 37. Based on 

 Ophiopeza yoldii Liitken (1859, Add. Hist. Oph., 2, p. 98) and sup- 

 posed to be distinguished by absence of supplementary oral plates 

 and concealment of radial shields. The species 0. yoldii thus be- 

 ]ongs in Pectinura as here used, and Ophiopsammus becomes 

 superfluous. 



There can. be no question as to the type-species of this genus, but unfortunately, 

 owing to the fact that it has not been met with since Forbes secured his single 

 small specimen, there is some room for doubt as to whether the radial shields in 

 that species are covered by the granulation of the disc or not. So far as I can 

 judge from Forbes's description and figure, the radial shields are not to be dis- 

 tinguished, save with difficulty, from the ordinary disc-scales, and like them are 



